AT&T Long Line Towers are the most distinctly recognizable microwave towers which are often abandoned. Google that.
Definitely be careful though. You don't want to find yourself on a microwave tower that's still turned on! It will cook you. If you really have the technical knowledge to understand the information, the FCC database of antennas is a great resource:
http://wireless2.f...strationSearch.jsp But for exploring purposes, the information on that site can be somewhat difficult to decipher. This is a huge topic, and there is a
lot to learn about it.
Do your research before trying anything!